Impacts of potential future sea level rise on the North branch of the Changjiang river estuary: Quantifying the saline water intrusion in the dry season

Abstract

The phenomenon of global sea level rise (SLR) is undeniable; the 4th IPCC report summaries that the\ud average rise rate of global is 1.8 mm/y since 1961. It is widely taken for granted that SLR will have a severe impact on\ud saline water intrusion processes in estuarine areas. In this paper, by using a two-dimensional hydrodynamic model\ud (MIKE21) and SLR scenarios of 0.5m, 1m and 2m, the impacts of potential future SLR on the North Branch of the\ud Changjiang River Estuary are evaluated by quantifying salinity changes in the dry season. The field data of tidal levels,\ud flow velocities and salinities are employed to validate the model, and the computed results match the observed values\ud well, which indicates that the validated model can provide reliable performances in reproducing the hydrodynamic and\ud saline water intrusion processes in the Changjiang River Estuary, then this validated numerical model was run with\ud present sea level as well as 0.5m, 1m and 2 m SLR scenarios in the dry season respectively. The computations show\ud that: i)the amplification of tidal levels in the upper reach of the South Branch is greater than that in the upper reach of\ud the North Branch with SLR; ii)the ebb and flood discharges in the upper cross-section of the North Branch both respond\ud to SLR with a significant increase trend, with the ebb flow split ratio of the North Branch increasing from 3.8% to\ud 10.3% in 2m SLR scenario; iii)the salinity in the North Branch presents a decrease trend with SLR, and the decreasing\ud extent in the upper reach is 11.4%-33.4%, which is obvious greater than that in the middle and lower reaches.\ud Consequently, it can be concluded that SLR enhances the ebb hydrodynamics and alleviates the saline water intrusion in\ud the North Branch